Potential reactivity of diabase, a basalt akin rock: microstructural approach

Abstract:

Several recent Works has been pointed out the potential of basalts to the alkali-aggregate reaction (AAR). Due to the difficulties of distinction, some relevant quarries in the São Paulo declare they are extracting basalt while they are actually extracting diabase. Although the difference between basalt and diabases is sometimes not easy to spot, it is important to AAR studies once diabases, as function of their formation process, usually show less volcanic gall, mesostasis or devitrified glass, considered as the main reactive phases in basalts. Six sample, considered as diabases by their geological context were selected from active quarries in São Paulo State. The samples were submitted to petrographic analyses and accelerated mortar bar test (Brazilian Standard NBR 15577:2008, Part 3 and 4). The results of the accelerated mortar tests indicate the potential alkali reactivity for three of the five studied quarries. The petrographic analyses showed that just one should be potentially reactive. The expansion of the other two is considered to be due a non-AAR effect, the swelling of clay minerals in response to the conditions imposed on the accelerated test.


Reference:
QUITETE, Eduardo Brandau; MENEZES, Priscila Melo Leal; MIRANDA, Angélica Oliveira. Reatividade potencial de diabásio, rocha semelhante ao basalto: abordagem microestrutural. In: CONGRESSO BRASILEIRO DO CONCRETO, 55., 2013, Gramado. Anais… São Paulo: IBRACON, 2013. 16 p

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